1. Field of the Invention
The present invention relates to telecommunication systems, and more specifically to a method and apparatus for conveniently determining the manner in which the wires connecting to a base set of a telephone system are used for transmission and reception of electrical signals representing a communication.
2. Related Art
Telephone systems are generally used for communication between users or machines as is well known in the arts. FIG. 1 depicts an example environment including telephone systems 101 and 102, which enable communication between two users. Telephone system 101 is connected to telephone system 102 by network 140. Telephone system 101 includes hand set 110 connected to base set 130 by wires 113, and telephone system 102 includes hand-set 170 connected to base 150 by wires 175. Users may use parts such as head sets instead of handsets while communicating with other uses. Parts such as hand-sets or head sets of a telephone system which are used by users for communication are referred to as user sets in the present application.
Network 140 may include one or more of PBXs, private networks, public networks and the like implemented in a combination of analog and/or digital transmission technologies as is well known in the relevant arts. Network 140 transfers signals between bases 130 and 150 to enable communication between users using hand sets 110 and 170.
In operation, in response to the voice of a user, hand set 110 generates electrical signals on wires 113. The voltage levels of the electrical signals on wires 113 generally represent the voice communication. In response to the voltage levels on wires 113, base set 130 generates transmission signals on line 113 according to a predefined interface protocol. Network 140 receives these transmission signals and delivers the signals to base set 150 also according to potentially a different pre-defined interface. Base set 150 converts the received signals to electrical signals, and transmits the electrical signals on wires 175 to hand set 170. The voltage levels of these electrical signals also generally represent the voice of the user of telephone system 101. The communication in the reverse direction from telephone system 102 to telephone system 101 is similarly described.
There are several situations in which it may be desirable to determine the voltage levels used on the wires 113 and 175 for representing voice communication. For example, the voice communication between telephone systems 101 and 102 of FIG. 1 may not be secure in the sense that an unknown third-party may be able to monitor and decipher (or modify) the communication anywhere between the two bases 130 and 150. Accordingly, one may wish to encrypt the communication for security.
One may further wish to encrypt the electrical signals on wires 113 between hand set 110 and base 130 as the encryption scheme can then be used in conjunction with bases which operate in both digital and analog modes. To clarify with an illustration, bases are typically designed to generate digital signals on line 134 when implemented for operation generally with private branch exchanges (PBXs), and are designed to generate analog signals on line 134 when implemented typically for operation directly with public switched telephone networks. In either case, the communication on wires 113 usually include analog electrical signals. For the encryption scheme to operate in both cases, one may wish to encrypt the communication by modifying the electrical signals on wires 113.
Encryption generally entails examining the electrical signals generated by hand set 110 and generating new electrical signals with different signal characteristics. The alteration of the characteristics makes it harder for one to decipher the communication represented by the electrical signals. The generation of new electrical signals generally requires a determination of the voltage levels of electrical signals received by base 130 such that the new signals generated can conform to the voltage levels with which base 130 is designed to operate. Therefore, it may be desirable to determine the voltage levels at which base 130 is designed to receive electrical signals.
When the encrypted signals are received by telephone system 102, the encrypted signals need to be decrypted such that sounds transmitted at hand set 110 can be reproduced at hand set 170. The decryption may also be performed between hand set 170 and base 150. The decryption processes may need to be implemented using the voltage levels of electrical signals generally used by base 150 in transmitting on wires 175. Accordingly, it may be necessary to determine the voltage levels used on wires 175 while electrical signals representing voice are being received.
Even though the need for determining voltage levels has been described with reference to transmission of voice signals from telephone system 101 to telephone system 102, it should be understood that the voltage levels may need to be determined while voice signals are transmitted in the reverse direction from telephone system 102 to telephone system 101.
Thus, there is a general need to determine the voltage levels used on wires connecting to telephone base sets at least while encrypting the communication signals.
In addition to determining the voltage levels, it may be necessary to determine the specific wires in 113 which are used for transmission, and which are used for reception. This need may be appreciated by considering a typical configuration in which four wires are present between each base and the corresponding user set. Two ("pair") of these wires are used for transferring of electrical signals in one direction (e.g, transmission) while the other two wires are used for transferring electrical signals in the other direction(reception). In general, there is no uniform convention as to which of the two pairs is used for transmission and which pair is used for receiving. Accordingly, it may be problematic to conveniently detect which wires are used for transmission and which wires are used for reception.
Several devices exist in areas such as telephone head-sets, in which a device is placed in the middle of wires 113. Due to the inability to meet one or more of the requirements noted above, users are generally required to perform manual configurations (such as setting switches) to enable the device to determine various parameters such as voltage levels and the precise wires which may be used for the transmission and reception of electrical signals representing voice communications. Unfortunately, manual configurations are undesirable in some situations at least for the reasons that they may be error prone and time consuming.
Accordingly, what is needed is a method and apparatus for conveniently detecting the various configuration parameters such as voltage levels used on wires connecting to a telephone base. The method and apparatus may also need to meet the requirements of any encryption technologies with which it may be implemented.